the sea transgressed, and calcareous sandstone, mudstone, and limestone were deposited in Oligocene times (34–24 Ma). Eocene coal measures crop out in the east, between Kerikeri and Waipu. Coal has been mined around Kamo, north of Whangarei. Limestone crops out around Whangarei, with an interesting display at the Waro Rocks Scenic Reserve, north of Hikurangi. Northland Allochthon In Early Miocene times (24–21 Ma), a series of thrust sheets was emplaced over Northland, extending as far south as the Kaipara Harbour and Albany areas. The rocks came from the northeast (perhaps beyond the Vening Meinesz Fracture Zone), and were emplaced in reverse order, but the right way up. The original rocks are of Cretaceous to Oligocene age (90–25 Ma), and include mudstone, limestone and basalt lava. These rocks outcrop around Silverdale, Warkworth, and Wellsford, reaching as far south as Albany. The allochthon includes displaced Te Kuiti group rocks. The basalt lava of the Tangihua Complex is believed to represent sea floor, that has been obducted onto Northland to form high standing massifs, such as the Reinga, Ahipara, Warawara, Mangakahia, and Maungataniwha massifs. Isolated bodies of serpentine occur at North Cape, and south of Maungaturoto. The Northland and East Cape Allochthons are assumed to constitute part of a single allochthon, that have later separated, due to the clockwise rotation of the eastern part of the North Island, relative to the western part. Early Miocene volcanism A subduction-related volcanic belt became active to the west of the current land in Northland in Miocene times (23 Ma), and gradually moved south down to Taranaki. It produced mainly andesitic stratovolcanoes. Most of these volcanoes have been eroded, but remnants form the Waipoua Plateau (basaltic, 19–18 Ma), and Waitākere Ranges (andesitic, 22–16 Ma). An eastern volcanic belt formed mainly andesitic volcanoes around Karikari (22.3–19.8 Ma), Whangaroa (20.5–17.5 Ma), Whangarei Heads (21.5–16.1 Ma), Bream Head, and created the Hen and Chicken Islands (19.5–16.5 Ma). Waitemata sandstone Miocene volcanoes and the Northland Allochthon eroded to form the Waitemata sandstone, between Whangarei and Auckland, on the eastern side of Northland. Uplift By middle Miocene, Northland was uplifted above sea level, with a slight westward tilt, exposing basement rocks on the eastern side, and resulting in a tendency for rivers to flow in a westerly direction. Recent basaltic volcanism Intra-plate basaltic volcanism has occurred in Northland from late Miocene to Quaternary times. The Kerikeri volcanic group covered the area from